Solvent treatment of hydrocarbon oils



Patented Aug. 5, 1941 UNITED stares PATENT OFFICE 4 2,251,773 ARBDNMeyer S. Agruss, Chicago, and Wesley H. Sowers,

Flossmoor, Ill., assignors to The Pure Oil Company, Chicago, 111., acorporation of Ohio No Drawing. Application January 12,1939,

Serial N0. 250,500

21 Claims.

This invention relates to extraction methods of refining mineral oilsand has particular reference to methods for extracting such oils bymeans of solvents whereby fractions of different chemical compositionthough of the same distillation range, are obtained.

It is well known in the art that mineral oils such as petroleum compriseessentially a mixture of various groups or homologous series ofcompounds such, for example, as paraffins, olefins, hydroaromatics,polymethylenes and other series of compounds of chain and/or ringstructure and in which the hydrogen to carbon ratio is less than in theaforementioned series. Crude petroleum oils are generally classifiedinto three types, namely, paraffinic, naphthenic and mixed base, whichcontain the various series of. hydrocarbons mentioned heretofore, invaryingpropcrtions. ,Probably the best known exam.-

ple of a parafiinic base crude oil is one obtained diate between theparaflinic and naphthenic base type crude oils. The parafiinic typecrude oils and their. distillatesmay be distinguished from thenaphthenic type crude oils and their distillates by certain arbitraryconstants used extensively in the oil refining industry.

The first of these constants is known as the viscosity index and is acoefficient based on the change of viscosity with temperature. This isdescribed by Dean and Davis, Chemical and Metallurgical Engineering,vol. 36, page 618, 1929.

The second of the constants referred to is the viscosity-gravityconstant. This is a constant expressing a relation between viscosity andspecific gravity and is described by Hill and Coates in Industrial andEngineering Chemistry, vol 20, page 641. V

The more paraffinic oils are characterized by relatively lowerviscosity-gravity constants and relatively higher viscosity indices,while the more naphthenic oils are characterized by higherviscosity-gravity constants and lower viscosity indices.

An object of the invention is to provide a method for separating viscousmineral oils into fractions by means of solvents.

Another object of the invention is to provide a method ,for increasingthe parafiinicity of min.- eral lubricating oils,

Still another object of the invention is to provide a new extractingagent for separating viscous mineral oils into paraffinic and naphthenicfractions.

' Other objects of the invention will be apparent from the followingdescription.

We have now found that oils containing both parafiinic and variousnaphthenic. hydrocarbons may be fractionally extracted with a selectivesolvent such as morpholine (tetrahydroparoxazine) and derivativesthereof such as those derivatives in which one or more hydrogen atoms inthe morpholine molecule is substituted by alkyl groups. As examples ofsuch derivatives may be mentioned ethyl tetrahydroparoxazine, l methyltetrahydroparoxazine, 1 butyl tetrahydroparoxazine and others. Thevarious series of hydrocarbons possess a different solubility in suchsolvent, the naphthenic hydrocarbons being much more soluble thereinthan the parafiinic hydrocarbons. When mineral oil containing bothseries of hydrocarbons is extracted with a solvent of the class aboveset forth, it is possible to effect a partial separation of theparafiinic from the .naphthenic hydrocarbons and to obtain a fractionwhich is more parafiinic than the original oil and one which is morenaphthenic. For example, from an oil of the mixed base type such as isfrequently found in the Mid-Continent area it is possible to produce anoil of a more paraffinic type such as is generally found in thePennsylvania oil fields. However, regardless of the source, it ispossible to obtain by our process oils which are respectively moreparafiinic and more naphthenic than the oils normally obtained from suchsource by distillation.

In accordance with our invention, the oil to be treated is first mixedwith morpholine or a suitable derivative of morpholine at suchtemperature that complete solution is effected. When the temperature ofthe mixture is reduced, a separation of the liquid into a two-layer.system will take place. One layer will contain a relatively small amountof the solvent dissolved in the paraffinic portion of the oil. This iscalled raffinate. The other layer will con.- tain the more naphthenicportion of the oil dissolved in the major quantity of the solvent. Thisis called the, extract, Thisprocedure may be conducted batchwise orcounter-currently. After the extraction, separation of the solvent fromthe oil may be effected by any one of a number of methods such asdistillation, extraction with water and sulfuric acid, or precipitationwith carbon dioxide or a carbon dioxide-containing gas. The two layersformed as a result of the extraction operation are of course, separatedprior to the removal of the solvent. This separation may be tion of thetwo layers by decantation. The yield of rafiinate was 52% by volume. Thesolvent was removed from both the raffinate and extract by distillationat room temperature. Tests on the original oil, raifinate and extractare all shown in Table III.

Example 2.100 parts by volume of the same lubricating stock was treatedwith four successive portions of 50 parts by volume of morpholine.

The extract was decanted before mixture of the raflinate with eachsuccessive portion of morpholine. Each batch of solvent was mixed withthe oil at a temperature of 180 F. and allowed to cool to approximately80 F. The two layers were separated by decantation and the morpholineseparated from both the rafiinate and the extract by distillation atatmospheric pressure. The yield of rafiinate was 67% by volume. Tests onboth the raffinate and the extract are shown in Table II. 7

TABLE II Rafilnate Extract Gravity 29. 3 19. 5 Vis./l 216. l, 671Vis./210 47. l 57. VI; 98 3 VGC .824 .884 Color 2% +7 Percent carbon res0.01 -0. 07

Example 3. 100 parts by'volume of 300 vis.

Gulf Coast lubricating distillate, the characterisaccomplished by anysuitable procedure, for ex- TABLE III ample, by decantation. Theextraction step may be repeated any desired number of times, each"Original 011 Raffinate Extract extraction producing an oil of higherparaffinicity, as may be evidenced by its higher viscosity. 2 4, 6,4index. Dewaxing may be effected either prior 380 385 375 420 425 430 orsubsequent to the extraction procedure. 307,3 249,2 405.0 The inventionwill be more clearly understood 1s 50 -10 from the following specificexamples. .887 .855 .916 Example 1.100 parts by volume of a lubricat- 3ing distillate obtained from a Mid-Continent oil, 003 0.01 ::I:: thecharacteristics of which are given in Table I, Was extracted threesuccessive times with 100 (B below) parts by volume of commercialmorpholine. The 20 mixture was first heated to a temperature of 140TABLE III- Cntmued F. and then allowed to cool to 120 F. whereupon atwo-layer system was formed. Cooling was Orlgmaloil Raffillate continuedto approximately F. and the two D 111 b'l't 130 F 220 1620 layers thenseparated by decantatlon. The sol 25 gfi zl hl g 1620 1620 vent wasremoved from the two layers by WaSh- Steam emulsion No 154 68 ing withwater, which was followed by a wash of 2% sulfuric acid and then a finalwater wash. A Tests after BrowmBovenageing 52% yield by volume ofrafiinate fraction was obtained. Tests on the original oil and the 30 o1 11 R fli t raffinate fraction are tabulated below: g 0 a m e TABLE ISludge (mgms./20O cc. oil); 11.

Acid N0 0.50. 0.05. Corrosion of copp str Positive Negative. Original iR ffi t 35 Steam jet test 25 minutes.. fiminutes.

20.7 31.4 From the foregoing data it is obvious that exig g 221 tractionof an oil with morpholine provides an 73 101 efiicient means ofseparating the oil into fractions 3% l-gig {U which are respectivelymore paraffinic and more NPA color +4 2/2 naphthenic than the originaloil. By repetition of the extraction process upon the rafiinate fractityof solvent to be used and the method of separating the solvent from theoil may varyconsiderably, depending upon the stock being treated and theequipment available with which to carry out the process but in generalthe ratio of solvent to oil will range from 1 to 5 parts of solvent byvolume to 1 part of'oil and the temperature of extraction from 125 F. to200 F. Separation of the solvent and oil into two distinct phasesgenerally occurs at about F. but this may vary greatly depending on thenature of the stock being treated.

In addition to the methods of separating the solvent from the oildescribed in the specific examples, morpholine may be readily separatedfrom oil at ordinary temperature by first contacting the morpholine withcarbon dioxide, forming a solid carbamate which may be easily separatedby filtration. Both the carbon dioxide and morpholine may be recoveredas such by simply heating the solid carbamate to a temperature of ap-'proximately 200 F. 7

1 It will also be noted from the data in Example 3 that treatment of a300 vis. Gulf Coast, oil with morpholine produces a rafiinate suitableas a high quality turbine oil. The sludging characteristics as shown bythe Brown-Boveri test are commensurate with high quality turbine o ilscommercially available. A consider-able improvement in the carbonresidue and color of the rafiinate is obtained which adds materially tothe desirable properties of oils treated by our method.

While the foregoing examples show the use of morpholine as -a selectivesolvent for hydrocarbon oils, derivatives of morpholine, particularlythose in which the hydrogen is replaced by an alkyl group, may also besuitably employed alone or mixed with each other or with morpholine. Theprocess is applicable to oils from all types of crude.

We claim:

1. In the solvent refining of mineral oils, the

process which comprises separating an oil con-' taining paraffinic andnaphthenic hydrocarbons into fractions respectively higher in paraflinicand naphthenic compounds by extracting said oil with compounds selectedfrom the group consisting of morpholine and its derivatives.

2. In the solvent refining of mineral oils, the process which comprisesadding compounds selected from the group consisting of morpholine andits derivatives to an oil containing parafiinic and naphthenichydrocarbons, heating the mixture to such temperature as to effectsolution, cooling the solution to form fractions respectively higher inparafiinic and naphthenic compounds and separating the two fractions.

3. Process in accordance with claim 2 where the added compound ismorpholine.

4. In the solvent refining of mineral oils, the process which comprisesadding compounds selected from the group consisting of morpholine andalkyl derivatives of morpholine to an oil containing paraffinic andnaphthenic hydrocarbons, heating the mixture to such temperature as toeffect solution, cooling the solution to form fractions respectivelyhigher in par-afiinic and naphthenic compounds, removing the fractionrich in naphthenic compounds and similarly retreating the fraction richin parafiinic compounds with said solvent.

5. Process in accordance with claim 4 where the added compound ismorpholine.

6. In the solvent refining of mineral oils, the process of producing amore parafiinic lubricating oil from a base oil of lesser paraflinicitywhich comprises bringing the oil into contact with compounds selectedfrom the group consisting of morpholine and alkyl derivatives ofmorpholine, thereby partially dissolving the oil, separating thesolution of oil so treated into fractions respectively more paraflinicand less par-aiiinic and removing the solvent from the treated oil.

7. Process in accordance with claim 6 where the compound is morpholine.

8. In the solvent refining of mineral oils, the process which comprisesbringing mineral oil containing paraffinic and naphthenic hydrocarbonsinto contact with compounds selected from the group consisting ofmorpholine and alkyl derivatives of morpholine, thereby effectingsolution in the solvent of a portion relatively higher in naphthenichydrocarbons, separating the solution so formed from the remainder ofthe oil and removing the solvent from both portions of the oil, therebyobtaining fraction-s of the oil respectively of higher paraffinic andnaphthenic hydrocarbon content.

9. Process in accordance with claim 8 where the oil is brought intocontact with morpholine.

10. Process in accordance with claim 8 where the solvent is removed fromboth portions of the oil by distillation.

11. Process in accordance with claim 8 whereby the solvent is removedfrom both portions of the oil by reacting the solvent with carbondioxide or a carbon dioxide-containing gas whereby a substantiallyinsoluble product is formed.

12. In the solvent refining of mineral oils, the process which comprisesseparating an oil containing parafiinic and naphthenic hydrocarbons intofractions respectively more paraffinic and more naphthenic than theoriginal oil by extracting said oil with morpholine.

13. Process in accordance with claim 12 where the morpholine is removedfrom both fractions by distillation.

14. Process in accordance with claim 12 where the morpholine is removedfrom both fractions by contacting the fractions with carbon dioxide orcarbon dioxide containing gas whereby relatively solid insolublecompounds are formed.

15. In the solvent refining of mineral oils, the method of increasingthe viscosity index of mineral lubricating oil distillate comprisingextracting the oil with compounds of the group consisting of morpholineand alkyl derivatives of morpholine whereby to separate fractions ofrespectively higher and lower viscosity index.

16. Method in accordance with claim 15 Where the compound is morpholine.

17. In the solvent refining of mineral oils, the method of increasingthe viscosity index of mineral lubricating oil comprising extracting theoil with compounds selected from the group consisting of morpholine andderivatives thereof in which hydrogen is replaced by alkyl groupswhereby to separate fractions of respectively higher and lower viscosityindex.

18. Method in accordance with claim 17 where the compound is ethyltetrahydroparoxazine.

19. Method in accordance with claim 17 where the compound is l butyltetrahydroparoxazine.

20. In the solvent refining of hydrocarbon oils, the process whichcomprises separating an oil containing paraflinic and non-paraflinichydrocarbons into fractions respectively higher in paraflinic andnon-paraffinic compounds by extracting said oil with solvent containingone or more compounds selected from the group consisting of morpholineand its derivatives.

21. Process in accordance with claim 20 where the solvent containsmorpholine.

MEYER S. AGRUSS. WESLEY H. SOWERS.

